/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.room.compiler.processing

import androidx.room.compiler.processing.javac.JavacElement
import androidx.room.compiler.processing.ksp.KSFileAsOriginatingElement
import androidx.room.compiler.processing.ksp.KspFileMemberContainer
import androidx.room.compiler.processing.ksp.KspTypeElement
import androidx.room.compiler.processing.ksp.wrapAsOriginatingElement
import javax.lang.model.element.Element
import kotlin.contracts.contract

/**
 * Represents an element declared in code.
 *
 * @see [javax.lang.model.element.Element]
 * @see XExecutableElement
 * @see XVariableElement
 * @see XTypeElement
 */
interface XElement : XAnnotated {

    /** The simple name of the element. */
    val name: String

    /** Returns the string representation of the Element's kind. */
    fun kindName(): String

    /**
     * When the location of an element is unknown, this String is appended to the diagnostic
     * message. Without this information, developer gets no clue on where the error is.
     */
    val fallbackLocationText: String

    /** The documentation comment of the element, or null if there is none. */
    val docComment: String?

    /** Returns true if all types referenced by this element are valid, i.e. resolvable. */
    fun validate(): Boolean

    /**
     * Returns the immediate enclosing element. This uses Element.getEnclosingElement() on the Java
     * side, and KSNode.parent on the KSP side. For non-nested classes we return null. For fields
     * declared in primary constructors in Kotlin we return the enclosing type, not the constructor.
     * For top-level properties or functions in Kotlin we return JavacTypeElement on the Javac/KAPT
     * side and KspFileMemberContainer or KspSyntheticFileMemberContainer on the KSP side.
     */
    val enclosingElement: XElement?

    /**
     * Returns the closest member container. Could be the element if it's itself a member container.
     */
    val closestMemberContainer: XMemberContainer
}

/** Checks whether this element represents an [XTypeElement]. */
// we keep these as extension methods to be able to use contracts
fun XElement.isTypeElement(): Boolean {
    contract { returns(true) implies (this@isTypeElement is XTypeElement) }
    return this is XTypeElement
}

/** Checks whether this element represents an [XEnumTypeElement]. */
fun XElement.isEnum(): Boolean {
    contract { returns(true) implies (this@isEnum is XEnumTypeElement) }
    return this is XEnumTypeElement
}

/** Checks whether this element represents an [XVariableElement]. */
fun XElement.isVariableElement(): Boolean {
    contract { returns(true) implies (this@isVariableElement is XVariableElement) }
    return this is XVariableElement
}

/** Checks whether this element represents an [XFieldElement]. */
fun XElement.isField(): Boolean {
    contract { returns(true) implies (this@isField is XFieldElement) }
    return this is XFieldElement
}

/** Checks whether this element represents an [XMethodElement]. */
fun XElement.isMethod(): Boolean {
    contract { returns(true) implies (this@isMethod is XMethodElement) }
    return this is XMethodElement
}

/** Checks whether this element represents an [XExecutableParameterElement]. */
fun XElement.isMethodParameter(): Boolean {
    contract { returns(true) implies (this@isMethodParameter is XExecutableParameterElement) }
    return this is XExecutableParameterElement
}

/** Checks whether this element represents an [XConstructorElement]. */
fun XElement.isConstructor(): Boolean {
    contract { returns(true) implies (this@isConstructor is XConstructorElement) }
    return this is XConstructorElement
}

/**
 * Attempts to get a Javac [Element] representing the originating element for attribution when
 * writing a file for incremental processing.
 *
 * In KSP a synthetic javac element will be returned, which allows us to pass originating elements
 * to JavaPoet and KotlinPoet, and later extract the KSP file when writing with [XFiler] if it
 * exists.
 *
 * Note that this function doesn't yet support Kotlin top-level functions and properties from
 * compiled classes in KSP due to https://github.com/google/ksp/issues/1704.
 */
internal fun XElement.originatingElementForPoet(): Element {
    return if (this is JavacElement) {
        element
    } else {
        // We use either the enclosing file or the class as the originating element for KSP.
        this.closestMemberContainer.run {
            when (this) {
                is KspTypeElement -> {
                    declaration.wrapAsOriginatingElement()
                }
                is KspFileMemberContainer -> {
                    KSFileAsOriginatingElement(ksFile)
                }
                else -> {
                    error("Originating element is not implemented for" + " ${this.javaClass}")
                }
            }
        }
    }
}
